Chemical Thermodynamics: Master the Fundamentals for Engineers

Question 1

For a closed system undergoing a spontaneous process, which statement correctly describes the changes in entropy and Gibbs free energy?

Accepted Answer

Entropy increases, and Gibbs free energy decreases.

Answer

Entropy decreases, and Gibbs free energy increases.

Answer

Entropy remains constant, and Gibbs free energy increases.

Answer

Entropy decreases, and Gibbs free energy decreases.

Question 2

The vapor pressure of a liquid is:

Accepted Answer

The pressure exerted by the vapor phase in equilibrium with its liquid phase.

Answer

The pressure required to convert the liquid completely into vapor.

Answer

The pressure at which the liquid boils at a given temperature.

Answer

The pressure at which the vapor condenses at a given temperature.

Question 3

A chemical reaction has a positive Gibbs free energy change (ΔG). What can you conclude about the spontaneity of this reaction?

Accepted Answer

The reaction is non-spontaneous at all temperatures.

Answer

The reaction is spontaneous at all temperatures.

Answer

The reaction is spontaneous at high temperatures only.

Answer

The reaction is spontaneous at low temperatures only.

Question 4

The change in free energy (ΔG) is related to the equilibrium constant (K) by:

Accepted Answer

ΔG = -RTlnK

Answer

ΔG = +RTlnK

Answer

ΔG = K/RT

Answer

ΔG = RT/K

Question 5

The fugacity of a pure component in a gas mixture is:

Accepted Answer

Equal to its partial pressure

Answer

Less than its partial pressure

Answer

Greater than its partial pressure

Answer

Not defined for pure components

Question 6

The standard Gibbs free energy of formation of a compound is:

Accepted Answer

The change in Gibbs free energy when 1 mole of the compound is formed from its elements in their standard states.

Answer

The change in Gibbs free energy when 1 mole of the compound is formed from its elements in any state.

Answer

The change in Gibbs free energy when 1 mole of the compound is formed from its ions in their standard states.

Answer

The change in Gibbs free energy when 1 mole of the compound is formed from its elements at any temperature.

Question 7

The Clausius-Clapeyron equation relates:

Accepted Answer

Pressure and temperature along a phase boundary

Answer

Entropy and temperature along a phase boundary

Answer

Volume and pressure along a phase boundary

Answer

Enthalpy and temperature along a phase boundary

Question 8

Which of the following is a characteristic of a spontaneous process?

Accepted Answer

ΔG < 0

Answer

ΔG > 0

Answer

ΔG = 0

Answer

ΔS < 0

Question 9

The heat of combustion of a fuel is:

Accepted Answer

The enthalpy change when 1 mole of fuel is completely burned in oxygen at constant pressure.

Answer

The enthalpy change when 1 mole of fuel is completely burned in air at constant pressure.

Answer

The enthalpy change when 1 mole of fuel is partially burned in oxygen at constant pressure.

Answer

The enthalpy change when 1 mole of fuel is completely burned in oxygen at constant volume.

Question 10

Identify the property that is NOT fundamental to a thermodynamic system.

Accepted Answer

Mass

Answer

Temperature

Answer

Pressure

Answer

Volume

Question 11

During an isothermal process, what is the change in entropy for the system?

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Indeterminate

Question 12

Identify the factor that does NOT influence the phase behavior of a substance.

Accepted Answer

Electric current

Answer

Temperature

Answer

Pressure

Answer

Composition

Question 13

Define the standard enthalpy change, ΔH°, for a reaction.

Accepted Answer

The enthalpy change when all reactants and products are in their standard states

Answer

The enthalpy change when only the reactants are in their standard states

Answer

The enthalpy change when only the products are in their standard states

Answer

The enthalpy change when neither the reactants nor the products are in their standard states

Question 14

Define the entropy of a system.

Accepted Answer

A measure of its disorder

Answer

A measure of its energy

Answer

A measure of its volume

Answer

A measure of its pressure

Question 15

Define the chemical potential of a substance.

Accepted Answer

The partial molar Gibbs free energy

Answer

The partial molar enthalpy

Answer

The partial molar entropy

Answer

The partial molar volume

Question 16

Consider the following equilibrium reaction: A(g) + B(g) <=> C(g) + D(g). If the concentration of A is increased, according to Le Chatelier's principle, which of the following will occur?

Accepted Answer

The equilibrium will shift to the right, increasing the concentration of C and D.

Answer

The equilibrium will shift to the left, decreasing the concentration of C and D.

Answer

The equilibrium will not be affected.

Question 17

In a closed system undergoing a reversible process, what is the entropy change of the system?

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Equal to the heat flow into the system divided by the system's temperature

Question 18

Identify the property that is NOT fundamental to a system.

Accepted Answer

Heat Capacity

Answer

Temperature

Answer

Pressure

Answer

Composition

Question 19

Define the heat capacity of a system.

Accepted Answer

Heat required to raise the temperature by 1 Kelvin

Answer

Rate of heat transfer to the system

Answer

Temperature at thermal equilibrium

Answer

Entropy change per unit temperature change

Question 20

Which is NOT a type of thermodynamic system?

Accepted Answer

Adiabatic

Answer

Open

Answer

Closed

Answer

Isolated

Question 21

What thermodynamic parameter is key to determining the spontaneity and direction of a chemical reaction?

Accepted Answer

Gibbs free energy

Answer

Enthalpy

Answer

Entropy

Answer

Internal energy

Question 22

Which property is NOT a fundamental thermodynamic property?

Accepted Answer

Work

Answer

Temperature

Answer

Volume

Answer

Enthalpy

Question 23

The change in Gibbs free energy for a reaction is equal to:

Accepted Answer

The change in enthalpy minus the product of temperature and entropy change

Answer

The maximum useful work that can be obtained from the reaction

Answer

The minimum amount of work required to drive the reaction

Answer

The heat transferred to or from the surroundings at constant volume

Question 24

Which of the following is NOT a type of phase transition?

Accepted Answer

Isothermal expansion

Answer

Melting

Answer

Condensation

Answer

Sublimation

Question 25

The standard enthalpy of formation of a compound is defined as:

Accepted Answer

The enthalpy change when one mole of the compound is formed from its constituent elements in their standard states

Answer

The enthalpy change when one mole of the compound is burned in excess oxygen

Answer

The enthalpy change when one mole of the compound is dissolved in water

Answer

The enthalpy change when one mole of the compound reacts with hydrogen

Question 26

Entropy is a measure of:

Accepted Answer

The randomness or disorder of a system

Answer

The heat transferred to or from the surroundings divided by the temperature

Answer

The change in internal energy divided by the volume change

Answer

The change in Gibbs free energy divided by the temperature

Question 27

The first law of thermodynamics implies that:

Accepted Answer

Energy cannot be created or destroyed, only transferred or transformed

Answer

The total entropy of an isolated system always increases over time

Answer

The enthalpy of a reaction is equal to the change in internal energy plus the product of pressure and volume change

Answer

The equilibrium constant of a reaction is equal to the ratio of the forward and reverse reaction rates

Question 28

Which of the following properties is NOT fundamental in thermodynamics?

Accepted Answer

Density

Answer

Temperature

Answer

Pressure

Answer

Volume

Question 29

The change in Gibbs free energy for a chemical reaction under constant temperature and pressure conditions is given by:

Accepted Answer

-RTln(Keq)

Answer

-RTln(Q)

Answer

RTln(Keq)

Answer

RTln(Q)

Question 30

Identify the characteristic of spontaneous processes:

Accepted Answer

Negative Gibbs free energy change

Answer

Positive entropy change

Answer

Negative enthalpy change

Answer

Positive Gibbs free energy change

Question 31

An equilibrium constant for a reaction is:

Accepted Answer

Ratio of activities of reactants and products

Answer

Ratio of forward and reverse rate constants

Answer

Ratio of partial pressures of reactants and products

Answer

Ratio of concentrations of reactants and products

Question 32

Which of the following is a phase diagram?

Accepted Answer

Plot of composition versus temperature

Answer

Plot of temperature versus pressure

Answer

Plot of enthalpy versus temperature

Answer

Plot of entropy versus temperature

Question 33

The critical point of a substance represents the point at which:

Accepted Answer

Liquid and gas phases become indistinguishable

Answer

Solid and liquid phases become indistinguishable

Answer

Liquid and solid phases become indistinguishable

Answer

Gas and solid phases become indistinguishable

Question 34

Enthalpy of mixing refers to:

Accepted Answer

Change in enthalpy when two or more components are mixed

Answer

Change in entropy when two or more components are mixed

Answer

Change in Gibbs free energy when two or more components are mixed

Answer

Change in volume when two or more components are mixed

Question 35

The Debye-Hückel theory explains:

Accepted Answer

Behavior of ions in dilute solutions

Answer

Behavior of gases at high pressures

Answer

Behavior of liquids near their critical point

Answer

Behavior of solids at low temperatures

Question 36

Which of the following phase transitions involves a decrease in entropy?

Accepted Answer

Freezing

Answer

Melting

Answer

Boiling

Answer

Sublimation

Question 37

What is the mole fraction of nitrogen in a gas mixture if the partial pressure of nitrogen is 0.3 atm and the total pressure is 1 atm?

Accepted Answer

0.3

Answer

0.2

Answer

0.4

Answer

0.5

Question 38

For an exothermic reaction, A(g) + B(g) -> C(g) + D(g), how will the equilibrium constant, K, change if the temperature is increased?

Accepted Answer

K will decrease

Answer

K will increase

Answer

K will remain constant

Answer

The sign of K will change

Question 39

Which of the following thermodynamic systems is an example of an open system?

Accepted Answer

A system exchanging heat and matter with its surroundings

Answer

A sealed container containing a gas

Answer

A flask containing a chemical reaction in progress

Answer

A system at constant temperature and volume

Question 40

The change in entropy of a closed system undergoing a reversible process is:

Accepted Answer

Zero

Answer

Always positive

Answer

Always negative

Answer

Unpredictable

Question 41

The Gibbs free energy change for a reaction is negative when:

Accepted Answer

The reaction is spontaneous

Answer

The reaction is non-spontaneous

Answer

The reaction is in equilibrium

Answer

The reaction is exothermic

Question 42

Which of the following factors does NOT affect the equilibrium composition of a chemical reaction?

Accepted Answer

Identity of the reactants

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 43

The enthalpy of formation of an element in its standard state is:

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Variable

Question 44

The critical point of a substance is the point at which:

Accepted Answer

The liquid and gas phases become indistinguishable

Answer

The solid and liquid phases become indistinguishable

Answer

The solid and gas phases become indistinguishable

Answer

The substance reaches its maximum entropy

Question 45

Which of the following factors **does not** affect the equilibrium constant of a reaction?

Accepted Answer

Volume of the reaction vessel

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 46

The standard enthalpy of formation of a substance is the:

Accepted Answer

Enthalpy change when 1 mole of the substance is formed from its elements in their standard states at 25 °C

Answer

Enthalpy change when 1 mole of the substance is formed from its elements in their standard states at 0 °C

Answer

Enthalpy change when 1 mole of the substance is burned in oxygen

Answer

Enthalpy change when 1 mole of the substance is dissolved in water

Question 47

Which of the following is the correct expression for the entropy of a perfect crystal at 0 K?

Accepted Answer

0

Answer

Infinity

Answer

Undefined

Answer

1 J/K·mol

Question 48

The heat capacity of a substance is:

Accepted Answer

The amount of heat required to raise the temperature of the substance by 1 K

Answer

The amount of heat released when the temperature of the substance decreases by 1 K

Answer

Independent of temperature

Answer

Always positive

Question 49

The Joule-Thomson coefficient is the:

Accepted Answer

Change in temperature of a gas when it undergoes an adiabatic expansion

Answer

Change in pressure of a gas when it undergoes an adiabatic expansion

Answer

Change in volume of a gas when it undergoes an adiabatic expansion

Answer

Change in enthalpy of a gas when it undergoes an adiabatic expansion

Question 50

The chemical potential of a substance in a mixture is the:

Accepted Answer

Partial molar Gibbs free energy of the substance

Answer

Partial molar enthalpy of the substance

Answer

Partial molar entropy of the substance

Answer

Partial molar volume of the substance

Question 51

Which of the following is a thermodynamic property that is NOT a state function?

Accepted Answer

Heat capacity

Answer

Enthalpy

Answer

Entropy

Answer

Gibbs free energy

Question 52

The spontaneity of a chemical reaction is primarily determined by:

Accepted Answer

The sign of ΔG

Answer

The sign of ΔH

Answer

The sign of ΔS

Answer

The magnitude of ΔH and ΔS

Question 53

The equilibrium constant for a reaction is a:

Accepted Answer

Constant that depends on both temperature and concentration

Answer

Constant that depends on temperature

Answer

Constant that depends on the concentration of reactants and products

Answer

Variable that changes with time

Question 54

The Clausius-Clapeyron equation primarily relates:

Accepted Answer

Pressure and temperature of a phase transition

Answer

Entropy and enthalpy of a phase transition

Answer

Gibbs free energy and volume of a phase transition

Answer

Heat capacity and specific heat of a phase transition

Question 55

The van der Waals equation of state is designed to account for:

Accepted Answer

Both intermolecular forces and finite molecular volume

Answer

Intermolecular forces

Answer

Finite molecular volume

Answer

Neither intermolecular forces nor finite molecular volume

Question 56

Fugacity is a measure of a substance's:

Accepted Answer

Tendency to escape from a mixture

Answer

Partial pressure at low concentrations

Answer

Independence from temperature and pressure

Answer

Relation to Gibbs free energy

Question 57

The equilibrium constant for a reaction is defined as:

Accepted Answer

The ratio of the activities of the products to the reactants

Answer

The ratio of the products to the reactants at equilibrium

Answer

The change in Gibbs free energy at equilibrium

Answer

The rate of the forward reaction divided by the rate of the reverse reaction

Question 58

The standard molar entropy of a substance is:

Accepted Answer

Its entropy at 298 K and 1 atm

Answer

Its entropy at 0 K and 1 atm

Answer

Its entropy at 1 atm and its boiling point

Answer

Its entropy at 298 K and the pressure at which it boils

Question 59

Which of the following is the ideal gas law?

Accepted Answer

PV = nRT

Answer

PV = NkT

Answer

PV/T = constant

Answer

nV/T = constant

Question 60

The entropy of a system is:

Accepted Answer

A measure of its disorder

Answer

A measure of its energy

Answer

A measure of its heat capacity

Answer

A measure of its temperature

Question 61

In thermodynamics, a closed system is characterized by:

Accepted Answer

Exchanging energy but not matter with the surroundings

Answer

Exchanging matter but not energy with the surroundings

Answer

Exchanging both energy and matter with the surroundings

Answer

Exchanging neither energy nor matter with the surroundings

Question 62

The thermodynamic function representing the maximum work that can be obtained from a closed system at constant temperature and pressure is:

Accepted Answer

Gibbs free energy

Answer

Enthalpy

Answer

Entropy

Answer

Helmholtz free energy

Question 63

The equilibrium constant of a chemical reaction signifies:

Accepted Answer

The extent of the reaction

Answer

The reaction rate

Answer

The mole ratio of reactants to products

Answer

The enthalpy change of the reaction

Question 64

The Clapeyron equation establishes the relationship between:

Accepted Answer

Temperature and pressure

Answer

Pressure and volume

Answer

Enthalpy and entropy

Answer

Gibbs free energy and temperature